Method for accomplishing one side expansion in pressure welded passageway panels



1961 J. H. DEDRICK 2,966,729

HOD FOR ACCOMPLISHING ONE SIDE EXPANSION IN MET PRESSURE WELDED PASSAGEWAY PANELS Filed May 31, 1956 ,:ll Q u Fig.2 Fig.3

INVEN TOR. JOHN H. DEDRICK BY Fig.4 Fig.5 MW

ATTORNEY United States Patent 1 O METHOD FOR ACCOMPLISI-IING ONE SIDE EX- IN PRESSURE WELDED PASSAGEWAY John H. Dedrick, Louisville, Ky., assiguor to Reynolds Metals Company, Louisville, Ky., a corporation of Delaware Filed May 31, 1956, Ser. No. 588,315

4 Claims. (Cl. 29-1573) This invention relates to pressure welded expanded passageway panels.

In some cases, it is desirable to expand a pressure welded passageway panel on one side or face only. Several methods for accomplishing one side expansion have heretofore been proposed but none has yet come into substantial use.

The principal object of the present invention is to provide a novel method of making pressure welded passageway panels which are expanded on one side only.

Another object is to accomplish one side expansion by utilizing the expansion force on the adjacent faces of a pair of superposed panels to neutralize each other.

Briefly, my method comprises: providing two pairs of foreshortened panel-forming sheets of metal, such as aluminum, each with a foreshortened passageway system pattern of stop-weld material interposed between the sheets; assembling both pairs in superposed relationship with an interposed foreshortened sheet of material separating one pair from the other, the separating sheet being weldable and elongatable under hot rolling conditions and having a lower melting point than that of the panelforming sheets; pressure welding the assembly into an integral elongated panel; simultaneously expanding both pairs along their stop-weld patterns to form passageway systems; and then heating the panel to soften the separating sheet sufliciently to enable one panel-forming pair of sheets to be separated from the other pair. During the expansion step the inner sheets of both pairs coupled with the separating sheet cooperate to form a solid 3-ply layer which resists expansion and thus tends to limit expansion to the outer sheet of each pair. This resistance to inside expansion can be substantially increased with the use of matched weld-resist patterns. By matched patterns I mean, of course, that the patterns match each other when assembled'so that, during the expansion operation, any tendency of the inner face of one pattern to expand is counteracted by the corresponding tendency of the inner face of the other pattern to expand in the opposite direction.

The invention will be described in greater detail in the following description taken in conjunction with the accompanying drawings wherein:

Fig. l is an exploded edge elevation of the assembly of sheets forming the panel;

Fig. 2 is an edge elevation of the panel assembly prior to pressure welding;

Fig. 3 is an edge elevation of the panel after pressure welding;

Fig. 4 is an edge elevation of the panel after the passageway expansion step; and

Fig. 5 is an edge elevation of the pair of panels formed. from the single panel after the separation step.

In accordance with the present invention, an assembly is formed of two pairs of foreshortened passagewayforming sheets 10, 11 of suitable material such as aluminum. A foreshortened passageway system or pattern of stop-weld material is interposed between each pair of 2,966,729 Patented Jan. 3, 1961 sheets 10, 11 in the same manner as provided in the conventional roll bonding process.

Before roll bonding these superposed pairs of foreshortened sheets of aluminum, an intermediate layer of pressure weldable separating material is arranged between them to complete the assembly. This assembly is pressure welded by heating and rolling to form an integral elongated S-ply panel having between the sheets of each pair, an elongated pattern of unbonded internal portions or areas corresponding to the correspondingly elongated pattern of stop-weld material and having between pairs a correspondingly elongated sheet of separating material. An expansion fluid is now introduced into the betweensheet space extending along each pattern of unbonded areas to stretch-expand them outwardly so as to form conduits or passages. Since roll bonding is well konwn, one process being disclosed in the Long patent, No. 2,662,273, further explanation is believed unnecessary.

Figs. 1 and 2 illustrate an intermediate layer 12 of material interposed between pairs of sheets 10 and 11. This layer 12 of material is selected from suitable materials having a melting point below that of the panelforming sheets 10 or 11 and above the temperature to which said sheets are heated for roll-bonding purposes.

Naturally the components making up the assembly of sheets 10, 11 and 12 will be precleaned prior to assembly so that their surfaces can be firmly bonded. After assembly, the layers will be spot-welded or otherwise secured to prevent shifting, heated and then roll-bonded while hot (800-950" F.) thereby forming an integral elongated panel 13 as illustrated in Fig. 3. This panel will contain one system or pattern of unbonded internal areas or portions between sheets 10 and another system or pattern of unbonded portions between sheets 11.

After the bonding or welding operation is completed, each system of unbonded internal areas is simultaneously placed under internal fluid pressure thereby forming expanded conduits or passages 14 extending from the opposite surfaces of the panel 13. Preferably this pressure expansion step will be performed between flat platens or plates in accordance with conventional roll bonding practice. Due to the use of flat platens, the outer surfaces, of the walls forming the tube conduits 14, will have the flats 15.

After the passage expansion step, the resulting expanded panel 13 is separated into a pair of panels 16 as illustrated in Fig. 5. This is done by heating the panel 13 to temperatures suflicient to soften or melt the separating sheet 12 whereupon the panel 13 may be separated into two pairs of panels 16.

In practicing this process, the patterns of stop weld material, forming the passageway conduits 14, may be identical or matched so that each component of one pattern will be positioned directly opposite the corresponding component of the other pattern. The passageway systems can then be simultaneously expanded with the same pressure thereby tending to minimize or overcome any tendency toward deformation of the areas of the panel 13 lying between the two passages 14. However, due to the thickness of the material between the pairs of conduits 14, little or no deformation may take place even when the two patterns are not matched.

When the sheets 10 and 11 are aluminum, having a relatively high melting point, the intermediate layer or separating sheet 12 may be 7 /z% silicon aluminum alloy. This silicon percentage may vary between 5% and 12%. When this type of material is used, the panel 13 can be roll bonded at temperatures of 800 F. to 950 F. since the melting point of 796% silicon aluminum alloy approximates l,070 F. The separation step could readily be performed at l,000 F. to 1,100 F.

As a further example, commercially pure zinc, having 3 amelting point of 700 'F., plus or minus, can be used to form the separating layer 12. Using this material the panel 13 can be rolled and bonded at. 400. to 700 F. and the separation step performed at 500 F. to 750 F. Since the lower melting points of .separating material necessitate the use of lower bonding temperatures and higher bonding pressures, I prefer to use separating materials whose melting points more closely approach the melting temperature of the panel-forming sheet material.

Having described my invention, 1 claim:

1. A method of making pressure welded expanded passageway panels comprising: providing two pairs of foreshortened panel-forming metal sheets, the sheets of each pair being in tace-to-face relationship with a foreshortened passageway system pattern of stop-weld material interposed between them; assembling both pairs in superposed relationship with a foreshortened layer of pressure Weldable separating material interposed therebetween and having a lower melting point than said panelforming sheets; pressure welding said assembly into an integral elongated panel at a temperature lower than the melting point of said separating layer; expanding the unbonded internal areas between the sheets of each pair of said integral panels to form passageway systems; and

4 separating one panel-forming pair from the other at a temperature lower than the .melting point of said panelforming sheet material.

2. The method according to claim 1 wherein: said panel-forming sheets are aluminum and said intermediate layer is a silicon aluminum alloy of a percentage between 5% and 12%.

3. The method according to claim 1 wherein: said panel-forming sheets are aluminum and said intermediate layer is commercially pure zinc.

4. The method according to claim 1 wherein: each passageway system pattern of stop weld material matches the opposite pattern.

References Cited in the file of this patent UNITED STATES PATENTS 

